Yesterday was Day 2 of having Kitteh at the house and things actually look like they are moving in a positive direction.
She spent the day while Mark and I were at work locked up in our bathroom and laundry room area, she seemed very comfortable in there and behaved herself while we were gone.
Eventually, at some point during the evening, she came out of the bathroom to be with us, and the dog, in the family room. Belle was a little less interested in what Kitteh was doing, which seemed to allow Kitteh to relax some. At one point, Belle had her head propped up on the couch about 2 inches from Kitteh, and Kitteh was just looking at her. There was no hissing, no obnoxiousness from Belle, they were both just nice and calm.
The situation is definitely no where near friendly between them, but I hope that this step in the right direction after 24 hours of knowing each other, foretells a future of - at least - coexistence between Belle and Kitteh.